diff --git a/lib/controller/checks.py b/lib/controller/checks.py
index c86593260..bdc76cd45 100644
--- a/lib/controller/checks.py
+++ b/lib/controller/checks.py
@@ -497,11 +497,11 @@ def simpletonCheckSqlInjection(place, parameter, value):
     firstPage, _ = Request.queryPage(payload, place, content=True, raise404=False)
 
     if not (wasLastRequestDBMSError() or wasLastRequestHTTPError()):
-        if getComparePageRatio(kb.originalPage, firstPage) > CONSTANT_RATIO:
+        if getComparePageRatio(kb.originalPage, firstPage, filtered=True) > CONSTANT_RATIO:
             payload = "%s AND %d>%d" % (value, randInt, randInt+1)
             payload = agent.payload(place, parameter, value, payload)
             secondPage, _ = Request.queryPage(payload, place, content=True, raise404=False)
-            result = getComparePageRatio(firstPage, secondPage) <= CONSTANT_RATIO
+            result = getComparePageRatio(firstPage, secondPage, filtered=True) <= CONSTANT_RATIO
 
     infoMsg  = "simpleton test shows that %s " % place
     infoMsg += "parameter '%s' might " % parameter
diff --git a/lib/core/common.py b/lib/core/common.py
index a1a5b13fc..dfda08e02 100644
--- a/lib/core/common.py
+++ b/lib/core/common.py
@@ -1954,9 +1954,17 @@ def unicodeToSafeHTMLValue(value):
     return retVal
 
 def getErrorParsedDBMSes():
+    """
+    Returns array with parsed DBMS
+    names till now
+    """
     return kb.htmlFp
 
 def showHttpErrorCodes():
+    """
+    Shows all HTTP error codes 
+    raised till now
+    """
     if kb.httpErrorCodes:
         warnMsg = "HTTP error codes detected during testing:\n"
         warnMsg += ", ".join("%d (%s) - %d times" % (code, httplib.responses[code]\
@@ -1964,7 +1972,16 @@ def showHttpErrorCodes():
           for code, count in kb.httpErrorCodes.items())
         logger.warn(warnMsg)
 
-def getComparePageRatio(firstPage, secondPage):
+def getComparePageRatio(firstPage, secondPage, filtered=False):
+    """
+    Returns comparison ratio between
+    two given pages
+    """
+    if filtered:
+        firstPage = getFilteredPageContent(firstPage)
+        secondPage = getFilteredPageContent(secondPage)
+
     conf.seqMatcher.set_seq1(firstPage)
     conf.seqMatcher.set_seq2(secondPage)
+
     return conf.seqMatcher.quick_ratio()